Exterior insulation finish systems (EIFS) are known in the art. Such systems typically consist of a layer of a substrate such as gypsum, an insulation layer (polystyrene, for example), mesh embedded in a coat of polymer and cement, and a polymeric finish. The polymeric finish can be applied in a variety of textures and colors to satisfy aesthetic requirements. Typical polymeric finishes comprise flexible acrylic latex compositions made by copolymerizing a high Tg monomer such as methylacrylate, ethyl acrylate, methyl methacrylate, etc. with a low Tg monomer such as butyl acrylate, hexyl acrylate, t-butyl acrylate, etc. These compositions are blended with sand to produce the finish. The mesh and polymer-modified cement layers can be applied in multiple layers.
Although such systems are said to be waterproof, problems are caused by water penetration through a variety of avenues such as cracks, joints and sealant failures. Problems include deterioration of the gypsum sheathing facer, loss of attachment of the system, corrosion or rotting of the structural members, spalling and delamination of the coatings and interior building damage. Where deterioration of the gypsum sheathing facer occurs, for example, the result can be the rotting of studs without any conspicuous signs of distress.
Care has been taken in the detailing of termination points such as sills, jambs, heads, parapets, scuffers, corners, and any opening or protrusion in an attempt to make them impervious to moisture. However, such detailing has proven time consuming and ineffective.
The use of waterproofing and vapor barrier membranes in interior insulation systems is known. The placement of the membrane is a function of the climate; the major consideration being that the dew point must occur where the resulting moisture condensation cannot penetrate the insulation. In cold climates, for example, the membrane is placed on the warm side of the insulation (i.e. between the insulation and interior finish) which prevents moisture condensation from penetrating the insulation. However, in regions where variations in climatic temperatures are significant, placement of the membrane to accommodate a colder exterior temperature will be inappropriate when the climate changes to warmer exterior temperatures. That is, in regions with varying climatic temperatures, the location where the dew point occurs and where the resulting moisture condensation forms in the building envelope varies. Heretofore, no suitable solution to the moisture condensation problem has been found.
U.S Pat. No. 3,411,256 discloses what is known in the art as an "upside down" roof. The upside down roof overcame the durability problems of the water impermeable membrane by adhering a layer of thermal insulation on the exterior side of the membrane. A protective layer is then employed to protect the insulating layer from sunlight. The protective layer can be water permeable.
U.S. Pat. No. 4,492,064 teaches a similar roof construction having channels to and in the evaporation of moisture through the insulation panels to the outside atmosphere. Thus disposed over a metal roofing deck is a fire-resistant barrier layer such as gypsum board, a water-permeable layer, a layer of thermal insulation material, and a water-permeable protective layer. The layer of insulation is unsecured to the water-permeable layer to allow for relative movement therebetween.